I have not seen anyone use it, but nothing prevents you from trying it. LESS is just a preprocessor that outputs CSS files, so the problems you might expect should be related to the Mozilla-specific CSS constructs you might need. I bet any such problems are not very difficult to fix.
On the other hand, if you are not working on something complicated than writing a topic from scratch, I would not expect LESS to provide sufficient benefits to justify an additional development step.
Nickolay
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